1. Field of the Invention
This invention relates to an image processing apparatus, such as a laser printer, having an electrophotographic photosensitive element.
2. Description of the Related Art
Owing to their high printing speed, quiet printing operation and excellent printing quality, printers such as laser printers having an electrophotographic photosensitive element have tended to find wider use in recent years in comparison with the conventional impact printers. Though conventional laser printers originally were high in price, costs have been lowered along with a reduction in size and weight, and such printers are now finding much greater use in the office and home.
A problem encountered with laser printers in many cases is that the user, upon pressing a printing starting button on a personal computer or the like, is made to wait a fairly long period of time before printing actually begins. More specifically, even when the printing starting button on a personal computer has been pressed, the printer (the printer machinery) does not operate immediately but begins operating upon passage of a prescribed period of time. This can cause the user to experience some anxiety.
The aforementioned problem is a result of the processing time needed by the image controller within the laser printer and the preparation time of the engine which relies upon electrophotography.
The image controller performs processing for converting code data, which is sent from the personal computer or the like, into a bit image. The requisite processing time differs depending upon the quantity of data sent from the personal computer but presently is on the order of several seconds to several minutes. A conceivable method of curtailing processing time is to raise the processing speed of the CPU which controls the image controller. However, such high-speed CPUs are extremely expensive and therefore are difficult to use in laser printers of the popular type at the present time.
As for the preparation time of the electrophotographic engine, a laser printer employs a thermal fixing device. In cases where the printer is shut down in order to conserve electric power, in many instances the thermal fixing device is turned off or the fixing temperature is set to be lower than that which prevails during operation. Accordingly, even if a print command is transmitted to the engine upon the completion of processing performed by the image controller, the engine will not start until the thermal fixing device attains a prescribed temperature at which fixing is possible. In addition, laser printers employ a motor for the scanning of a polygon mirror, and the printing operation will not be carried out until the motor attains a prescribed rotational speed. Thus, the engine requires a prescribed preparation time and will not operate until this time elapses, even if a start signal is received from the image controller.